


Universal Gravitation

by talia_ae



Category: The Avengers (2012), Thor (2011)
Genre: F/M, Fluff, Humor, Isaac Newton - Freeform, Romance, Science, Strip Tease, do it for science, physics is amazingsauce
Language: English
Status: Completed
Published: 2012-06-11
Updated: 2012-06-11
Packaged: 2017-11-07 12:00:21
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 1,166
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/430935
Author URL: https://archiveofourown.org/users/talia_ae/pseuds/talia_ae
Summary: <blockquote class="userstuff">
              <p>Bruce tries to teach Darcy physics.  Darcy tries to distract him.  It ends up being a win-win situation for them both.</p>
            </blockquote>





	Universal Gravitation

**Author's Note:**

> er, the physics in this is (hopefully) correct, as I got it from memory. I did have to look up the exact value for the gravitational constant, though. Go reference tables!

"So," Bruce says.  He's standing in front of a whiteboard, dry erase marker in her.  Darcy's sprawled in a chair a few feet away from him, a spiral-bound notebook in her lap.  She's tapping her pen against her lip, eyeing him thoughtfully.  "I think it's best if we start with Newton.  Do you, uh, what do you know about him?"  
  
Darcy looks up at him, eyelashes fluttering under the lens of her glasses.  He knows she has contacts, and that she almost definitely chose the glasses on purpose.  "Sat under a tree.  Apple fell.  Boom, gravity was invented!"  
  
"Well," Bruce says.  "Discovered.  It was discovered.  You can't invent gravity."  
  
"Pretty sick if you could patent it though," Darcy points out.  Bruce nods.  
  
"Yeah, whoever could manage that would be richer than Tony could ever dream of being.  Okay, so Newton comes up with three laws of motion, obviously a brilliant guy, and we use these for a lot of things, especially mechanics.  First law is that the velocity of a body, an object, whichever you want to call it, that velocity is constant until acted upon by an external force."  
  
"So like, friction," Darcy says, picking up the pen in front of her.  Face contemplative, she sticks it into her hair, winding her braid into a bun.  It's warm in the room, or maybe that's just him.  "Right?  That's the point of brakes and so on?"  
  
"Exactly," Bruce says.  "So an ideal ball in a frictionless vacuum could roll on forever.  The next is that net force equals mass times acceleration.  This one is pretty easy, you use it for a lot of basic physics problems, but complicated ones as well, you just derive from it."  
  
Darcy nods.  "And the third?"  
  
"The third law is that for every action, there's an equal and opposite reaction."  
  
"Why it hurts if you punch someone."  She leans forward, giving Bruce an excellent view of her cleavage.  He swallows.  
  
"Yeah.  They're hitting you back with just as much force, even if they're not actually, you know, hitting.  It's also why banging your head against the wall hurts too."  
  
"Might be a good thing for SHIELD agents to know," Darcy says dryly.  Bruce laughs.  
  
"Right.  So the thing about Newton's laws is that at a certain point, you can't use them.  They get superseded by special relativity-- that's Einstein, at least initially.  Classical mechanics, Newton, that all gets contradicted, though it takes a couple hundred years.  Doesn't mean Newton's laws are useless, and relativity-- that's all the weird space time stuff-- we'll get into that quite a bit later, it's sort of jargony."  
  
Darcy stretches, and he allows himself a moment to admire the elegant line her body makes, almost a perfect sine curve.  "So for every new topic, I should take off a piece of clothing."  
  
Bruce swallows, hard.  "I think we'd both get pretty distracted pretty quickly if you did that."  
  
"Mmm, kinda the point."  She unbuttons her sweater; he's both thankful and disappointed to see that she's wearing an opaque camisole underneath.  "I just want to let you know, I have a bunch of dirty jokes about fluid mechanics ready and waiting."  
  
"Good to hear," Bruce responds.  "Fluid mechanics get weird, though, just a warning-- and I'm sure you have something to say about that, but save it, please.  It's the same for particle physics, you'll really have fun when we cover the nature of light.  So let's stick with mechanics for now.  This is where we have free-body diagrams.  Basically, you draw something, then draw the magnitude and direction of the forces acting on it."  He turns, sketching a quick example on the whiteboard.  "Always gravity-  and force of gravity, Fg, generally equals mg, mass times gravity.  That g is 9.81 meters per seconds squared on Earth.  If you drop something, that's what it's accelerating towards the ground at."  
  
"Cool," Darcy says, and drops her pencil, eyes following the trajectory down.  It clacks when it hits the floor, and Bruce grins.    
  
"That g is lowercase.  Big G, uppercase, is the universal gravitational constant.  It's in the reference table I printed out for you, but I can tell you it now.  It's hard to measure exactly, but the latest approved numerical value is 6.67384 times 10^-11 Newtons times meters per kilogram squared.  You use this to find the attractive force between two bodies."  
  
Darcy grins, and it's unabashedly wicked.  "So you could use big G to find the attractive force between, say, you and my breasts.  For example."  
  
"Big G times both respective masses, divided by the distance between us squared," Bruce says, almost automatically.  "Infinitesimal, in theory.  In practice, it's a pretty big attraction."  
  
Darcy bites her lip, considering, and then pulls off her top.  Her bra is purple, with lime green polka dots, and Bruce _knows_ she did that on purpose.  She leans a little, and if he looks closely-- and he's definitely looking closely-- he can see the faint outline of her nipple against the lavender lining of the bra.  That's something he's interested in pursuing.  
  
"Richard Feynman-- and yes, I looked him up, you have like three different posters of him all over your lab, plus Tony has at least twice that many, which is just a little bit ridiculous, I think he's thinking of taking up the bongo drums just like his idol-- once said that 'physics is like sex. Sure, it may give some practical results, but that’s not why we do it'.  Penny for your thoughts?"  Another wicked grin, and a glance at him from under lowered eyelashes.  "Doctor Banner?"  
  
"Both are enjoyable," Bruce says, and yup, he definitely walked right into that one, judging by the wink she throws him.  He drops his whiteboard marker and bends to pick it up, staunchly trying to ignore Darcy's wolf-whistle (and she has got to stop spending so much time with Tony Stark).  "Anyways.  What was I talking about?  Universal gravitation, big G, right.  So it comes from Newton also, classical mechanics way back in the 1600s.  The law is the equation I just told you, which--"  
  
"Does this count as a topic change?" Darcy asks.  "Should I take off my pants?"  
  
Her hands go to the button of her jeans, slipping it open, and then to the zipper.  At the sound it makes, Bruce pauses.  Looks her over, spread out in the chair with her shirt and cardigan discarded in a puddle on the floor and her jeans stuck around her left ankle.  Her underwear matches her bra, except that it's lacier.  He reconsiders, thinks of how soft her lips are, the feeling of her hair wound around his hands, how perfectly she feels when she's pressed up against him, arms around his neck. He stares at the picture she makes right now, lovely, half-naked, and almost decadent in the desk chair.  
  
"I think it's time for a lunch break," Bruce says decisively.  Darcy cheers and unhooks her bra.  
  


 


End file.
